1. Field of the Invention
The present invention relates to an identification sequence issuing device for an identification sequence that is issued for the verification of the identity of an individual and an identification sequence verification device that verifies the identification sequence, and the present invention particularly considers error detection and error correction at the input of the identification sequence without giving a sense of unnaturalness in operation.
2. Description of the Related Art
The identification sequence method is an indispensable method to recognize a particular user in a card system, a payment system or the like, and finds applications in a diversity of fields.
In the card system, identification sequence information is written on a card, and is authenticated by an identification sequence a user can easily remember. On the other hand, in a payment system in which service is provided to a particular user, authentication is typically performed by transmitting to the user an identification sequence for verifying the identity of the user, and by allowing the user to input the identification number or identification sequence.
The identification sequence used in the payment system requires a larger-number of digits than the card system. To help the user remember the identification sequence, it may include letters, such as ABC and the like, in addition to numbers.
When the user inputs the identification sequence, a system conventionally performs an all-number search for the identification sequences issued to determine whether the input identification sequence agrees with any of the issued identification sequences.
If the identification sequence has a large number of digits, it is subject to an error in transmission, and the user is likely to input an erroneous number. For this reason, when an identification sequence issued, a redundancy is provided to the identification sequence.
As an example of the prior art, Japanese Unexamined Patent Publication (Kokai) No. 4-40128 uses an identification sequence that is made of an increment identification sequence with a redundancy bit added.
FIG. 8 is a block diagram of a device that generates such a prior art identification sequence with a redundancy added, in which there is shown an increment ID sequence generating means 14 for generating an increment identification sequence, for example, using a counter or the like, and a redundancy bit generating means 15 for adding a redundancy bit to the increment identification sequence generated by the increment ID sequence generating means 14.
The prior art identification sequence having a redundancy comprises an original identification sequence portion and a redundancy portion added thereto. For example, the prior art redundancy bit generating means 15 can provide for the correction an error of 1 bit in the identification sequence by generating a check bit of the systematic code of a Hamming code of a generating polynomial g(x)=x.sup.3 +x+1.
FIG. 9 is a diagram showing the method of generating identification sequences with redundancy represented by sets, in which the number of elements of increment identification sequences that are a source corresponds to the number of identification sequences with redundancy added.
The authentication is conventionally performed as above, and has the following problems.
Firstly, since the prior art adds a redundancy bit to an increment identification sequence, the identification sequence is in principle expressed by a bit format or a number only. This makes an identification sequence difficult for a user to remember.
Secondly, since, in the prior art, the identification sequence is of fixed length and the increment identification sequence length and redundancy bit length of the increment ID sequence generating means are fixed, then error detection and correction capabilities are fixed regardless of the number of issued identification sequences. A identification sequences greater length than the length of identification sequences generated by the increment ID sequence generating means 14 cannot be issued.